Manufacture of trithio ortho esters of carboxylic acids



OF C

l 1 i screen or 'rnrro on'rno EST one some .lo David Kendall, iliord, England, assignor to liiord Limited, Mord, England, a company ol Great Britain No Drawing. Application March 24, 1943, Serial No. 480,333. In Great Britain April 20, 1942 where R is a. hydrocarbon group) can be readily prepared by the condensation of formic acid or formic esters with merceptan in the presence of hydrochloric acid as condensing agent. This method fails when applied to acids other than formic acid.

The usual method of making ortho-esters is the action of on alcohol on an imino-ether hydrochloride but an analogous process for producin trithio ortho esters based on the use of e mercapten instead of an alcohol entirely fails. Thus.

ecetimino-thio-ethyl ether hydrochloride is compietely unaffected by weeks of treatment with ethyl mercapten.

No general method has hitherto been described for producing tri-thio ortho esters of acids other than formic acid and it has now been discovered, end this forms the heels of the present invention, that trithlo ortho esters of such other acids may he prepared by e general process which conslots in the condensation of s. mono-thio-ester of the general Formula, 1

RnCQfiRe (1) R COfiRs ZRafiH -9 IRA-053R! H3O s3; where R1 end R2 have the mess essigned to them sleeve and R: is e hydrocerhongroup.

The mono-thio-ester of general Formuie i may he prepared by any or the known processes, e. g.

siredto produce a. trithio ortho ester in which the ester radicles are all of the some cherecter, to carry out the whole reaction in one stage, without isolating the mono-thio-ester. Thus one molecular equivalent of the sold halide (preferably the acid chloride) may be condz-swith three molecular equivalents (or more) of the mercepton in the presence of o strong dehydrating agent such as anhydrous zinc chloride, occur-ding to the equation:

Again, instead of using the acid helide, the origi nel acid may be employed, RLdQQTfi.

In both the processes described-in the preceding paragraph it is believed that theinono-thloester RLCOSRZ is termed es en intermediate end both these processes ore therefore to be considered as falling within the scope or the present invention.

The reaction may he effected using ell types oi. merceptens, for example, eliryl, erelhyl end eryl mcrcaptens. end the invention may he epplieci to the production of the trithio-ortho esters o2 hoth aliphatic and cyclic end both seturntecl end unsetureted oerboxyiic acids. In the case of the unsaturated acids it is preferable first to nrepere the trithio-ortho ester of e saturated cold con teining readily removehle substituents which on removal leave the desires unsetureted acid Thus, to obtain the trithio-ortho ester oil ecryiic acid it is preferable to start with =chlornropic ecid end prepare the trithio ortho ester oil such ecid, subsequently removing the element oi" in drochloric acid to convert the s eluor-proplonic by interaction of on acid heiide with n niercopten eooordlng to the equation:

R1. CO.X+RQSH R1.CO.SRQ+

(where X is ehalogen atom). In this reaction no 11; agent need be employed. Hovm since this reaction is also eflected by treatment with e mercepten it is possible, where it is de residue to an acrylic residue.

By employing an originel sold or sold halide which contains more than one carbonyl or can boxylic helide group, e. g. melonic or succinic acids or acid chlorides and higher homologues or this series, products may he obtained which contein more then one trithio ortlio ester group.

The term "ecid halide" when H;- to the acid hshde of an orsenic cerboxylic sold in the specification and 0 means compounds which hev'e e hydrocarbon radical attached to one, two, etc., redicels of the formula where R1 the above e;

iollo =1 ezemplee illustrete the invention way.

but are not to be regarded as limiting it in any 100 ccs. of ethyl mercaptan was mixed with 23.5 ccs. of acetyl chloride, the reaction mixture being cooled in an ice bath. About 5 gms. or anhydrous zinc chloride was added and this promoted a vigorous reaction with the evolution of hydrochloric acid gas. Further zinc chloride was then added to a total or 90.5 gms. and the mixture was allowed to stand for 24 hours with occasional shaking. The mixture was then poured into 150 cos. of an ice/water mixture. Zinc chloride remaining in the reaction vessel was dissolved in a little dilute hydrochloric acid and added to the ice/water mixture. A layer of oil separated out and this was removed and extracted with successive lots of ether. The combined ether extracts were washed with water,- and with sodium carbonate solution and dried over potassium carbonate. The ether was then removed from the dried extracts by evaporation on a water bath and the dry residue was distilled in vacuo. The product was obtained as a liquid boiling at 121 C. at 10 mm. pressure.

The same product was obtained, though in smaller yield, by reacting 100 cos. of mercaptan, 18 ccs. of acetic acid and 90.5 gms. of zinc chloride. The mixture was allowed to stand for 24 hours and the product separated as before.

lar to that of Example I using 11.6 cos. of benzol chloride, 30 cos. of ethyl mercaptan and 27.2 gms. of anhydrous zinc-chloride. The product was obtained as. a liquid boiling at 188 C. at 12 mm.

pressure. Exmn: IV

Preparation of mono-ethnl-dibenzyl-trithioortho-dcetate 7.06 cos. of acetyl chloride and 1.2 cos. of ethyl mercaptan were mixed together and refluxed on a water bath for three hours. .Ethyl thio acetate, boiling at 116 C. was then separated from the reaction mixture by distillation.

11.4 gms., of ethyl-thio-acetate as thus prepared was mixed with 28.5 ccs. of benzyl mercaptan and 29.8 g'ms. of anhydrous zinc chloride .was carefully added. The reaction mixture became warm and gradually thickened. After allowing the mixture to stand for 48 hours it was poured into an ice/water mixture whereupon the product separated as an oily layer. This was purified as in Example! and the product was thus obtained as a dark red oil boiling at 210-215? C. at mm. pressure with some decomposition.

Emma: V Preparation of trithio-ethill-ortho-acrirlate 51 gms. of p-chlorpropionyl chloride and 133 ccs. of ethyl mercaptan were heated together for cc. of ethyl mercaptan. After allowing to stand 3 hours. The mixture was then cooled and 109 gms. of anhydrous zinc chloride were gradually added. The mixture was then allowed to stand for 24 hours during which time it thickened to a yellow oil. This was poured into an ice/water mixture and the product which separated was purified as in Example I. This product consisted mainly of trithio-ethyl-ortho-B-chlor propionate and had a boiling range from 1.40-160 C. at 10 mm. pressure.

10.7 gms. of sodium was dissolved in 160 ccs. of ethyl alcohol and the cooled solution was mixed with 60 gms. of trithioethyl ortho-p-chlor propionate prepared as above. The reaction mixture became warm and sodium chloride separated. The mixture'was heated on a water bath for one hour and was then cooled and poured into 500 ccs. of an ice/water mixture. The product separated as an oily layer and this layer was extracted with ether and the ether extracts were washed with water and dried over anhydrous sodium sulphate. The ether was then evaporated and the residue distilled in vacuo yielding the desired tri-thio-ethyl-ortho-acrylate as a yellow oil boiling at l49-150 C. at 10 mm. pressure.

Exmnx VI Preparation of bis-trithio ethyl ortho succinate 31 gms. of succinyl chloride and ccs. of ethyl mercaptan were mixed with cooling (using an icesalt freezing mixture) and the reaction solution was allowed to stand for 24 hours, protected from atmospheric moisture by means of calcium chloride guardtubes. 109 gms. of anhydrous zinc chloride was then added cautiously with cooling and the mixture allowed to stand for a further 48 hours. It was then poured onto cracked ice to which some dilute hydrochloric acid had been added. The prepicitated oil was separated by ether extraction; the ether extracts were washed with water and 10% sodium carbonate solution, and then dried over anhydrous potassium carbonate. The ethereal solution was concentrated and the residue distilled in vacuo, yielding the product as a yellow oil having boiling point 222 C. at 15 mm. pressure.

Exusru VII Preparation of bis-trithio ethyl ortho adipate 18.3 gms. or adipyl chloride was mixed (with cooling in an ice-salt freezing mixture) with 80 overnight, 54.4 gms. of anhydrous zinc chloride was cautiously added in small portions with cooling and the reaction mixture allowed to stand for 24 hours. By the same procedure as in Example V! the product was obtained as a yellow oil having boiling point 260 C. at 12 mm. pressure.

Enron VIII Preparation of bis-trithio ethyl ortho malonate 14.1 ms. or malonyl chloride and 60 cc. of ethyl mercaptan were mixed with good cooling and allowed to stand for 24 hours. 54 gms. of anhydrous zinc chloride was added in portions, at 0 0., and the reaction mixture allowed to stand for 56 hours. By the same treatment as in Example VI the product was obtained as a yellow oil having boiling point -5 C. at 5 mm. pressure.

The trithio ortho-esters produced according to the present invention are useful as intermediates in the production of other organic compounds, for

in sulphones.

assaiss What I claim is:

1. s for the production ester of an organic carboxylic acid having an unsubstituted saturated hydrocarbon radical attached to the carbonyl group which comprises condensing a mono thio ester of the said acid with a mercaptan in the presence of a strong inorganic dehydrating agent. Y

2. Process for the production of a trithio ortho ester of. an organic carboxylic acid having an unsubstituted saturated hydrocarbon radical attached to the carbonyl group which comprises condensing a mono thio ester of the said acid with a mercaptan in the presence of zinc chloride.

3. Process for the production of a trithio ortho ester of an organic carboxylic acid having an unsubstituted saturated hydrocarbon radical attached to the carbonyl group which comprises condensing an acid halide of the said acid with at least three molecular equivalents of a mercaptan in the presence of a strong inorganic dehydrating agent, whereby a mono-ester of the said acid is formed in situ and reacts with further mercaptan to produce the desired trithio ontho ester.

4. Process for the production of a trithio ortho ester of an organic carboxylic acid having an unsubstituted saturated hydrocarbon radical attached to the carbonyl group which comprises condensing an acid halide of the said acid with at least three molecular equivalents of an alkyl mercaptan in the presence of a strong inorganic dehydrating agent, whereby a mono-ester of the said acid is formedin situ, and reacts with further alkyl mercaptan to produce the desired trithio ortho ester. v p I 5. Process for the production of a trithio ortho ester of an organic carboxylic acid having an unsubstituted saturated hydrocarbon radical attached to the carbonyl group. which comprises condensing an acid chloride oi the said acid with of a trithio ortho at least three molecular equivalents of a mercaptan ill-the presence or a strong inorganic dehydrating agent, whereby a mono-ester of the said acid is formed in situ and reacts with further mercaptan to produce the desired trithio ortho ester.

6. Process for the production of his trithio ortho ester of dicarboxylic acids having an unsubstituted saturated hydrocarbon radical attached to the carbonyl groups, which comprises condensing an acid halide of said acid with at least six molecular equivalents of a mercaptan in the presence of a strong inorganic dehydrating agent, whereby a his mono thio ester of the said acid is formed in situ and reacts with further mercapten to produce the desired bis trithio ortho ester.

7. A process for the production of trithioethyl-ortho-acetate which comprises condensing acetyl chloride with at least three molecular equivalents of ethyl mercaptan in the presence of anhydrous zinc chloride, whereby a monothio ester of acetic acid is formed in situ and reacts with further ethyl mercaptan to produce trithioethyl-ortho-acetate.

8. A process for the production of trithioethylortho-propionate which comprises condensing propionyl chloride with at least three molecular equivalents of ethyl mercaptan in the presence of anhydrous zinc chloride, whereby a monothio ester of propionic acid is formed in situ and re-- acts with further ethyl meroaptan to produce trithioethyl-ortho-propionate.

9. A process for the production of bis-trithioethyl-ortho-succinate which comprises condensing succinyl chloride with at least three molecular equivalents of ethyl mercaptan in the presonce of anhydrous zinc chloride, whereby a thio ester of succinic acid is formed in situ and reacts JOHN navm KENDA L. 

